What is missing?

[SpikeCapri]

Can anyone tell me what part is missing from my carb?

[Bug]

Nothing!
Some models had an anti-stall diaphragm there, so the engine could be run leaner (if it started to die, the increased vacuum acted on the diaphragm and gave a little squirt of fuel to wake it up again)
The carb bodies were all made to the same pattern, but not all had that fitted. As long as it runs ok you don't have anything missing.

[SpikeCapri]

That is good news, but is it meant to piss out fuel? It's not squirtig out or anything but rather slowly dripping

[Bug]

That is good news, but is it meant to piss out fuel? It's not squirtig out or anything but rather slowly dripping

No its not! That suggests your carb was originally one with the antistall diaphragm fitted. Those without it didn't have the drillings opened out.
So, it looks like you need to either find the bits needed to re-instate the antistall system, or probably better, make up some kind of blank and seal to close it off.
You could just get hold of the correct cover and fit a antistall diaphragm, but not connect the vacuum pipe to it. This will seal it ok.
Maybe chat to Caprigear and see if he has any old carbs you could cannibalise?

[metalheaven]

Could just fill holes with some chemical metal, resistant to fuel. Few times i have used it
to fix a hole in a tank